Oxidative dehydrogenation of aliphatic hydrocarbons over aluminum phosphate supported molybdenum and vanadium



United States Patent Ofilice 3,320,331 Patented May 16, 1967 3,320,331OXIDATIVE DEHYDROGENATION F ALI- PHATIC HYDROCARBONS OVER ALUMI- NUMPHUSPHATE SUPPORTED MOLYB- DENUM AND VANADIUM Noel J. Gaspar and IsraelS. Pasternak, Sarnia, ()ntarro, Qanada, assignors to Esso Research andEngineering Company, a corporation of Delaware No Drawing. Filed Jan.27, 1966, Ser. No. 523,268 19 Claims. c1. zen-sass This inventionrelates to a novel catalyst system for the oxidative dehydrogenation ofaliphatic hydrocarbons and in particular relates to a novel catalystsystem for the oxidative dehydrogenation of parafiins. Moreparticularly, this invention relates to a novel catalyst systemcomprising a major amount of aluminum phosphate and a minor amount of aheavy metal oxide selected from the group consisting of (a) molybdenumoxide, (b) vanadium pentoxide, and (c) a combination of (a) and (b).Still more particularly, this invention relates to a process for theoxidative dehydrogenation of aliphatics, which comprises contacting analiphatic feed and oxygen in a reaction zone at a temperature of betweenabout 900 F. and about 1300 F. with a catalyst comprising a major amountof aluminum phosphate and a minor amount of a heavy metal oxide selectedfrom the group consisting of (a) molybdenum oxide, (b) vanadiumpentoxide, and (c) acombination of (a) and (b).

It is known in the prior art that aliphatic materials can be convertedto more highly unsaturated materials by various dehydrogenation methods.One such well-known commercial method is the Houdry process. Thisprocess is a thermal dehydrogenation of paraflins to olefins andhydrogen over a chromia alumina catalyst and is subject to thermodynamiclimitations. For example, the reaction is carried out at hightemperatures under vacuum, which results in a large and expensivereactor system. Conversions per pass are low, requiring a large recyclewhich expands recovery facilities and reactor sites. In addition, thehigh rate of coke lay-down requires frequent catalyst regenerations withthe associated spare reactor and complex system of pipes and valves. Thenet result is a high investment with high operating costs.

It is further known that aliphatic materials can be dehydrogenated inthe presence of halogen promoters and catalysts. While such processesare capable of producing good yields of unsaturated compounds, theyrequire the utilization and regeneration of relatively expensivehalogens.

In accordance with the present invention, aliphatics, such as lightparafiins, are contacted with an oxygencontaining gas in the presence ofa novel catalyst to form olefins and water. As water is a very stableproduct thermodynamically, the reaction is not equilibrium limited andatmospheric pressure can be employed. Moreover, the oxygen in the feedgas keeps the catalyst free of coke and catalyst regeneration issubstantially eliminated.

It is, therefore, an object of the present invention to provide a novelcatalyst for the oxidative dehydrogenation of aliphatic materials. Afurther object of the present invention is to provide a catalyst for theoxidative dehydrogenation of paraffins, such as light parafl'ins.

A still further object of the present invention is to provide a processfor the catalytic oxidative dehydrogenation of aliphatic materials toolefins and water.

The exact nature, substance and objects of the present invention will bemore clearly perceived and understood by referring to the followingdescription and claims.

It has now been discovered that aliphatic materials can be catalyticallydehydrogenated by contacting an aliphatic feed and an oxygen-containinggas in a reaction zone at a temperature of between about 900 F. andabout 1300 F. with a catalyst comprising a major amount of aluminumphosphate and a minor amount of a heavy metal oxide selected from thegroup consisting of (a) molybdenum oxide, (b) vanadium pentoxide and(c), a combination of (a) and (b).

Aliphatic feed stocks which can be dehydrogenated by the present processinclude paraffins and olefins containing between 2 and 20 carbon atoms.Preferably, the aliphatic feed is a hydrocarbon material containingbetween 2 and 8 carbon atoms and more preferably, is a paraffincontaining between 2 and 6 carbon atoms. Especially preferred are thelight or normally gaseous hydrocarbons, such as ethane, propane, butane,butene, isobutane, isobutene and the like; and the normally liquidhydrocarbons such as pentane, pentene, isopentane, isopentene, hexane,hexene, octane, octene and the like.

The oxygen employed as feed in the present process can be supplied tothe reaction zone in any readily usable form. Conveniently, oxygen issupplied as an oxygen-containing gas, e.g., air, which contains betweenabout 19 and about 21 weight percent oxygen. While it is preferable toemploy air, oxygen-enriched air having more than 21 weight percentoxygen can be employed. Furthermore, an inert diluent such as nitrogenand/ or steam can be used to lower the oxygen content of theoxygen-containing gas to below 19%. In general, the mole ratio of oxygento aliphatic feed can vary between about 0.25:1 and about 1.5:1 andpreferably, is about 1:1.

The novel catalytic system employed in the present process fordehydrogenating aliphatics to olefins and water comprises aluminumphosphate doped with one or more heavy metal oxides selected from thegroup consisting of molybdenum oxide and vanadium pentoxide. The amountof heavy metal oxide admixed with the aluminum phosphate can vary over awide range. In general, the present catalytic system comprises a majoramount of aluminu-m phosphate and a minor amonut of molybdenum oxide,vanadium pentoxide, or a combination of the two. Thus, the heavy metals,as their oxides, can amount to between about 1 and about 49 mole percentof the total active catalyst specie. Preferably, the aluminum phosphateis doped with between about 2.5 and about 10 mole percent of said heavymetal(s) in the form of their oxides. More preferably, the aluminumphosphate is doped with about 5 mole percent of said heavy metal(s).Amounts over about 10 mole percent do not produce substantially improvedresults.

With respect to the catalyst comprising aluminum phosphate and a minoramount of molybdenum oxide, it has been found that best results areobtained when between about 2.5 and 5.0 mole percent molybdenum, as itsoxide, is employed. In addition, it has further been found that the blueform of molybdenum oxide (probably M0 0 produces better results thanthat obtained with the use of the fully oxidized form of molybdenumoxide (M00 When the catalyst specie employed is that of aluminumphosphate doped with a minor amount of vanadium pentoxide, it has beenfound that best results are obtained when between about 5 and about 10mole percent of vanadium, as its pentoxide, is employed.

In the case where the catalyst specie employed comprises aluminumphosphate doped with a minor amount of a mixture of molybdenum oxide andvanadium pentoxide, it has been found that best results are obtainedwhen the amount of the mixed metals to aluminum phosphate is betweenabout 2.5 and about 10 mole percent, preferably about 5 mole percent. Inpreparing the mixed metal oxides of molybdenum and vanadium, the moleratio of vanadium to molybdenum in the mixture can vary over a widerange. In general, the mole ratio of vanadium to molybdenum can varybetween about 20:1 and about 1:20, preferably between about 9:1 andabout 1:9 and more preferably is about 4:1.

In general, the amount of catalyst employed to dehydrogenate thealiphatic feed varies over a wide range and is more or less determinedby the design of the reactor.

The catalyst species employed in the present process can be prepared inany conventional manner. For example, aluminum phosphate and the heavymetal oxide(s) can be dry-mixed; slurried with water; dried; pelleted,calcined; and crushed into granules for use. In another convenientmethod, aluminum phosphate can be soaked in a solution of the requiredamounts of the ammonium salts of the heavy metals employed. Thissolution is then evaporated to dryness and the solid ground up, pilled,calcined and crushed.

Dehydrogenation of aliphatics in accordance with the present process canbe carried out in any suitable reaction vessel. A typical example ofsuch a reaction vessel is a riser-type reactor. The reactor can containeither a fixed or fluidized catalyst bed. However, since the oxidativedehydrogenation of aliphatics is an exothermic reaction, the use of afluidized catalyst bed is preferred. In addition, any conventionaltechniques designed to prevent the formation of a temperature build-upin the catalyst bed, e.g., catalyst dilution with low surface area inertmaterial or the spreading-out of the catalyst in a large number of smalldiameter, parallel, fixed-bed tubes can be employed with advantage.

The present oxidative dehydrogenation process is generally carried outat temperatures of between about 900 F. and about 1300 F., preferablybetween about 1100 F. and about 1200 F. The pressure within the reactionzone is not critical and will generally be atmospheric pressure;however, superatmospheric pressures such as between about 5 and about100 p.s.i.g. can be successfully employed.

The space velocity of the hydrocarbon in the dehydrogenation reaction isdependent upon the temperature at which the reaction is performed. Thehigher the temperature employed, the shorter the required contact time.In general, the space velocity of the hydrocarbon feed will vary betweenabout 0.25 and about 3 weights of hydrocarbon per weight of catalyst perhour (w./w./hr.), preferably, the space velocity will be between about0.5 and about 1.5 w./w./hr. and more preferably will be between about0.5 and about 1.0 w./w./hr. Contact times will, accordingly, varybetween about 0.2 and about seconds.

In a typical process scheme, aliphatic feed and air, meteredindividually through rotameters, are mixed and passed into a stainlesssteel reactor in an electrically heated tube furnace. The reactants arepreheated over inert beads and passed into the reaction zone filled withcrushed (10-20 mesh) catalyst. Dehydrogenated products leave thefurnace; are quenched in a water-cooled condenser; go into a separatorwhere the liquid products are removed and the gas is either vented orcollected in, for example, a plastic balloon. Samples can be taken fromthe balloon for gas chromatographic analysis. Orsat analysis, as well asdensity and volume measurements, can be taken on the balloon contentsand from these measurements a weight balance for the run and a completeanalysis of the products can be calculated. For fluid beds, 40-60 meshgranules of catalyst can be employed.

The present process is more particularly described in the followingexamples which are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art.

In the following examples, catalyst species were prepared as follows:

(A) ALUMINUM PHOSPHATE Aluminum phosphate was prepared by dissolvingaluminum nitrate in dilute nitric acid, adding a stoichiometric quantityof phosphoric acid and neutralizing with ammonium hydroxide. Theprecipitate was filtered, washed and dried.

(B) ALUMINUM PHOSPHATE-MOLYBDENUM OXIDE CATALYSTS Aluminum phosphate wasdoped with molybdenum by mixing with dry molybdenum oxide (M00 ormolybdenum blue (M0 0 slurrying with water, drying, pelletting andcalcining at 11001200 F. for about three hours. Molybdenum blue wasprepared by the method described by Schirmer et al., The Composition andStructure of Molybdenum Blue, J.A.C.S., 64, 2543 (1942).

(C) ALUMINUM PHOSPHATE-VANADIUM CATALYST Aluminum phosphate was dopedwith vanadium in accordance with the procedure described above withrespect to molybdenum (paragraph B) except that vanadium pentoxide wasemployed in place of the molybdenum oxide.

(D) ALUMINUM PHOSPHATE (MOLYBDENUM- VANADIUM) CATALYSTS Themolybdenum-vanadium on aluminum phosphate catalysts were made in thefollowing manner. Molybdenum trioxide and vanadium pentoxide were mixedtogether in a mortar in the desired proportions. The mixture was heatedin a muflie furnace and fused. After cooling, the solid mass was crushedto a fine powder. The required amount of this powder was dry-mixed withpowdered aluminum phosphate, slurried with water, dried, pelleted,calcined at 11001200 F. for about three hours and crushed into 10-20mesh granules for use in the reactor. For fluid bed runs, a 40-6O meshfraction was used.

(E) Aluminum phosphate was doped in accordance with the proceduresdescribed in paragraph B above with niobium (as No O chromium (as Cr Oand tungsten (as tungsten blue, W O prepared by the reduction of sodiumtungstate with zinc and HCl).

Example 1 (Runs 1-2) In the following runs, an n-butane-air feed waspassed over a fixed catalyst bed at atmospheric pressure in a oneinchstainless steel tubular reactor. Butane space velocity was about 1w./w./hr.; the reaction temperature was about 1100 F.; and the moleratio of oxygen to n-butane was about 1:1. The aluminumphosphate-molybdenum oxide catalyst was prepared in accordance with theabovedescribed procedures by adding molybdenum oxide to an aqueousslurry of aluminum phosphate so as to give 2.5 mole percent molybdenumon the aluminum phosphate. The slurry was mixed thoroughly and dried at230 F. The resulting dried product was calcined at 1200 F. in air forthree hours and crushed into 1020 mesh granules for use in the reactor.Thirty cubic centimeters of catalyst were charged to the reactor. Theresults of runs 1-2 are found in Table I.

TABLE I Selectivity to C4 Olefin at 35% n-C; Conversion, Mole percentPercent Increase in Catalyst Selectivity 1 All-P04 2 AlPO4-2.5 molepercent Mo as M00 3,320,331 a p 6 Example 2 (Runs 3-9) The data of TableIII show that the optimum concentration of vanadium for maximum activitywas about 10 mole percent. At this level, selectivities were about 50%improved over those for pure aluminum phosphate. 5 No appreciableimprovement in yield or selectivities is obtained by doping above themole percent level.

In Runs 35, an n-butane feed was dehydrogenated in the fixed bed reactorof Example 1 and in a fluid bed reactor made of one-inch vycor glasstubing employing aluminum phosphate and aluminum phosphate doped with2.5 mole percent molybdenum as molybdenum blue as the catalyst species.In Runs 6 9, a l-butene feed was sub- Example 4 (Runs 1549) ected todehydrogenation with the alumlnum phosphatemolybdenum blue catalyst.Reaction conditions and re- Aluminum phosphate was doped at the 3, 5, 7and 9 sults are summarized in Table II. 10 mole percent level with amixture containing vanadium TABLE IL-CONVERSION OF BUIANE ANDBUTENEo'tlxgfLTgl i lglEs AND BUTADIENE WITH 2.5% Mo(BLUE) ON AIPO.

Selectivity, mole percent Conver- Run N 0. Catalyst Bed Temp, F. HC SV,Of/HC slon, 1

(Temp. max. F.) w./w./hr. Ratio mole Butadiene to percent To C4- To C4=Butenes in Product (a) Butane Feed' 3 AlPOi Fixed... 1.100 (1,170) 1 110.3 0 6 A1Po.+2.5% Mo (Blue) -.do. 1,100 (1,100) 1 1 12.8 0 5 .doFluid... 1,100 (1,130) 1 1 19.9 1 1 Fixed 800 (1.020) 1.5 1 40.5 Fluid.1,100 (1,145) 2 1 44.4 do 1,100 (1,100) 2 1.5 42.3 do 1,200 (1,200) 3 15 38.3

*As air.

The data of Table II show that the addition of molybpentoxide andmolybdenum oxide such that the mole ratio denum blue increased theselectivity to olefins from buof vanadium to molybdenum was 4 to 1.These catalysts tang b b t 5 1.()% itho t changing the ratio of wereused for the oxidative dehydrogenation of n-butane butadiene to butenesin the products. In going to a fluid in the l-lnch stainless steelreactor of Example 1. The bed, only a slight increase in the over-allolefin selectivity catalyst was prepared in the manner describedhereinwas observed, but the ratio of butadiene to butenes in the above.Reaction conditions and results of Runs 1519 product was doubled. With abutene feed, about a 5% are summarized in Table IV.

TABLE IV.OXIDATIVE DEHYDROGENATION OF n-BUIANE WITH 80 V-20 1H0 LIIX ONALUMINUM PHOS- PHATE CATALYST Catalyst 111104 Temp, F. Conversion,Selectivity to Olefin Yield, Bntadiene/ Run No. Doped w1th (Temp, max.F.) percent C4 Olcfins, mole percent Butene in mole percent Product 15,100 (1,176) 34. 6 28. 6 9. 9 0.6 16. 3 mole percent (80 Y/20Mo)- 1,100(1,150). 39. 7 32. 9 13. 1 0.2 17. 5 mole percent (80 V/20 Mo) 1,100(1,183) 39. 6 30. 4 15.6 0.15 18" 7 mole percent (80 V/20 Mo). 1,100(1,100) 40. 0 39.1 15.6 0.15 19 H 9 mole percent (80 V/20 Mo) 1,100(1,190) 41. 6 37. 1 15.4 0.16

*As air.

increase in selectivity at constant conversion was observed The datacontained in Table IV show that the addition when going from a fixed toa fluid bed. of 3 mole percent of the /20 V/Mo mixture to the Example 3(Runs 1044) aluminum phosphate resulted in an increase in olefin lselectivity at constant conversion. Five mole percent of Alllimlnllm P QP doped W1t h Vanolls amollms of the vanadium-molybdenum mixture causeda further in- Vanadlum PentoXlde, Was Prepared 1n accordance Wlth thecrease in olefin selectivity; however, no further increase methoddescribed hereinabove. This catalyst was then 6 in selectivity wasobtained above the 5 mole percent level. employed in Runs 11-14 todehydrogenate n-butane 1n a similar reactor to that employed inExample 1. A run Example 5 (Runs 20-24) with aluminum phosphate as thecatalyst was also performed for comparison purposes. Results are sum-Mixtures of vanadium pentoxide and molybdenum marized in Table III. 65oxide with vanadium/ molybdenum molar ratios of 10,

TABLE III.-DEHYDROGENATION OF n-BUTANE ON ALUMINUM PHOSPHATE-VANADIUMCATALYST Run Temp, F. HO SV 04 Conversion, Selectivity to No. Catalyst(Temp, max. F.) w./w./hr. OWHC percent 0 Olefins,

mole percent 10 AlPO4 1,100 (1,165) 1 1 32. 4 22. 5 11 ARCH-2.5% V as V1, (1, 150) 1 1 37. 3 24. 6 12 AlPO4+5% V as V20s 1,100 (l, 165) 1 1 38.4 34. 0 13 AlPO4+10% V as V205 1, 100 (1, 1 1 37. 9 34. 2 14 A1PO4+25% Vas V 05 1, 100 (1, 1 1 37. 1 29. 5

*As air.

'7 8 75/25, 50/50, 25/75 and 10/90 respectively were preand the yieldsof olefins were increased. The data in pared in accordance with theprocedures outlined here- Table VI further shown that in the fiuid 'bedruns employinabove. These mixtures were each doped, at the mole g anoXygen/hydroearhen mole ratio of 1, the relative percent (V-l-IvIo) l l,onto l i phosphate and amount of butadiene to butene in the product wasgreatly were employed as catalysts for the oxidative dehydrogena- 5increased tion of n-butane. Reaction conditions and results of runsExample 7 (RIMS 2024 are summarized in Table V. In order to compare thecatalytic activity of other TABLE V.OXIDATIVE DEHYDROGENATIDgpXEkgBUTANE VARYING V/Mo RATIO ON A1PO4 [n04 Space Velocity=0.5 w./\v./hr.;Of/HC Feed Mole Ratio=1/1] Catalyst AIPO' Temp, 1(Temp. Conversion,Selectivity to Olefin Yield, Butadiene/ max.

Run No. Doped with percent C4 Olefins, mole percent Butene in 5% otmolepercent Product 20 (90 V/ l\/Io)c 1,100 (1,172) 31.1 41.0 12. 8 0. 24(80 V/ Mo) 1,100 (1,183). 39. 6 39. 4 15. (i 0.15 (75 V/ IVIO) 1,100(1,135)-.- 31. 9 40. 7 13.0 0.16 N50 Mo). 1,100 (1,170) 33.0 48. 5 16. 00.18 (25 V/ Mo) 1,100 (1,145) 1 35.1 36. 5 11.5 0.23 24 (10 V/ Mo) 1,100(1,177) n 39. 0 42.0 16. 4 0.36

*As air. From Table IV. The data of Table V show that no substantialdifference heavy metal oxides from Groups V-B and VI-B of the in resultswere obtained by varying the mole ratio of Periodic Table with that ofvanadium, aluminum phos- Vanadium t0 molybdenum Over a Wide range in a25 phate was doped with the oxides of vanadium, niobium, Y Specieemploying 5 mole Percent of the resPective chromium and tungsten inaccordance with the proce- Ihlxturesdures outlined hereinabove. Thesecatalysts were em- Example 6 (Runs 25'27) ployed in a 1-inch stainlesssteel fixed bed reactor for the In an attempt to decrease thetemperature rise i the oxidative dehydrogenation of n-butane. Reactioncondicatalyst bed, a l-inch Vycor reactor with a fluidized bed 30 tionsand results are tabulated in Table VII.

TABLE VII.CATALYTIC ACTIVITY OF GROUPS V-B AND VI-B OXIDES ON AlPOiCatalystGroups V-B and Temp., F. (Temp, HC SV Conversion, Selectivity toYield, VI-B max. F.) w./w./l1r. Of/I-IC percent C4 Olefins, percent molepercent Run N0.

AlPOi 1 1 31.6 31. 4 9. 9

AIPO1+4% Or as crro 1 1 48.0 21. 0 10.1

A1PO1+2.5% Nb as Nbz 1 1 44. 0 20. 5 9. 0

31.. AiPo,+2.5% v as V05. 1 1 53.3 26.1 13.9

32 A1Por+2.5% W as wroum. 1 1 40.9 15.1 6.2

*As air.

of 5 mole percent (SUV-20 Mo) on aluminum phosphate The data containedin Table VII show that chromium catalyst was employed to effectoxidative dehydrogenation and niobium had very little effect on theyields compared of n-butane. Conditions and results of Runs 25-27 are 45with aluminum phosphate; vanadium gave a marked imsummarized in TableVI. provement; while tungsten definitely depressed yields.

TABLE VI.OXIDATIVE DEHYDRO GENATION OF n-BUTANE FLUID BED RUNS WITH 5%(80 V/20 Mo) ON AlPOr CATALYST Run Ten1p., F. (Temp, HC SpaceConversion, Selectivity Yield mole Butadiene/ No. Max. F. Velocity,Or*/EIC percent to C1 Olefins, percent Butenes in w./\v./hr mole percentProduct As air.

The data of Table VI show that better participation is Example 8 (Runs33-34) obtained in a fluid bed than in a fixed bed. In the fixed bedreactor, an oxygen/hydrocarbon mole ratio of 1.5 50 In Order furtherShow the uniqueness of the Present caused temperature rises in thecatalyst bed of between catalyst System, an alumina Catalyst wascompared with 250 and 300 F. Moreover, the yields of olefins werealuminum Phosphate in a manner Similar to Example generally lower thanthose of a lower oxygen/feed con- The alumina Catalyst Was P p y heatingI Y- centration. However, in the fluid bed, temperature rises d e u nat0 1600 F. for eight hours. Reaction of only 6075 F. were observed atthese conditions, 55 conditions and results are summarized in TableVIII.

TABLE VIIL-COMPARISON OF CATALYTIC ACTIVITY OF ALUMINUM PHOSPHATE ANDALUMINA FOR OXIDATIVE DEHYDROGENATION OF n-BUTANE Temp, F. HO SV, 04Conversion Selectivity Run No. Catalyst (Temp, max. F.) w./w./hr. OzlHCpercent to C4 Olefins, mole percent 33 A 1,100 (1,165) 1 1. 5 50.6 7.334 A1PO4" 1,100 (1,165) 1 1. 5 46. 6 18.1

The data of Table VIII show that the alumina catalyst was very activefor burning and cracking reactions; but, resulted in a very lowselectivity to olefins as compared to the aluminum phosphate catalyst.

While the above examples have been illustrated by employing n-butane andn-butene as the aliphatic feed, it is to be noted that the instantlydescribed novel catalyst and process are equally effective for otheraliphatic feeds, e.g., those described hereinabove.

While there are above-described a number of specific embodiments of thepresent invention, it is obviously possible to produce other embodimentsand various equivalent modifications thereof without departing from thespirit of the invention.

Having set forth the general nature and specific embodiments of thepresent invention, the true scope is now particularly pointed out in theappended claims.

What is claimed is:

1. A process for the oxidative dehydrogenation of aliphatichydrocarbons, which comprises contacting an aliphatic feed and oxygen ina reaction zone at a temperature of between about 900 F. and about 1300F. with a catalyst comprising a major amount of aluminum phosphate and aminor amount of a heavy metal oxide selected from the group consistingof (a) molybdenum oxide, (b) vanadium pentoxide, and (c) a combinationof (a) and (b).

2. A process according to claim 1 wherein said aliphatic feed is a C Chydrocarbon.

3. A process according to claim 1 wherein said aliphatic feed is a C Cparafiin.

4. A process according to claim 1 wherein said dehydrogenationtemperature is between about 1100 F. and about 1200 F.

5. A process according to claim 1 wherein said catalyst is aluminiumphosphate doped with between about 2.5 and about 10 mole percent of saidheavy metals in the form of their oxides.

6. A process according to claim 1 wherein said catalyst is aluminumphosphate doped with between about 2.5 and about 10 mole percent of amixture of molybdenum and vanadium in the form of their oxides, the moleratio of vanadium to molybdenum being about 20:1 and about 1:20.

7. A process according to claim 6 wherein said mole ratio of vanadium tomolybdenum is between about 9:1 and about 1:9.

8. A process according to claim 1 wherein said molybdenum oxide is theblue form of molybdenum oxide having the empirical formula, M 0

9. A process according to claim 1 wherein the mole ratio of oxygen toaliphatic feed is between about 0.25:1 and about 15:1.

10. A process according to claim 1 wherein the aliphatic hydrocarbonfeed is passed through the reaction zone at a space velocity of bet-weenabout 0.25 w./w./hr. and about 3 w./w./hr.

11. An oxidative dehydrogenation catalyst consisting essentially of amajor amount of aluminum phosphate and a minor amount of a heavy metaloxide selected from the group consisting of (a) molybdenum oxide, (1))vanadium pentoxide, and (c) a combination of (a) and (b).

12. A catalyst according to claim 11 wherein said aluminum phosphate isdoped with between about 2.5 and about 10 mole percent of said heavymetals in the form of their oxides.

13. A catalyst according to claim 11 wherein said aluminum phosphate isdoped with between about 2.5 and about 10 mole percent of a mixture ofmolybdenum and vanadium in the form of their oxides, the mole ratio ofvanadium to molybdenum being between about 20:1 and about 1:20.

14. A catalyst according to claim 13 wherein said mole ratio of vanadiumto molybdenum is between about 9:1 and about 1:9.

15. A catalyst according to claim 11 wherein said molybdenum oxide isthe blue form of molybdenum oxide having the empirical formula M0 0 16.A process for the oxidative dehydrogenation of n-butane, which comprisescontacting n-butane and oxygen in a reaction zone at a temperature ofbetween about 1100 F. and about 1200" F. with a catalyst comprisingaluminum phosphate doped with about 2.5 mole percent of molybdenum asits oxide.

17. A process for the oxidative dehydrogenation of n-b-utane, whichcomprises contacting n-butane and oxygen in a reaction zone at atemperature of between about 1100 F. and about 1200 F. with a catalystcomprising aluminum phosphate doped with about 2.5 mole percent ofmolybdenum as molybdenum blue.

18. A process for the oxidative dehydrogenation of n-butane, whichcomprises contacting n-butane and oxygen in a reaction zone at atemperature of between about 1100 F. and about 1200 F. with a catalystcomprising aluminum phosphate doped with about 5 mole percent of amixture of vanadium and molybdenum in the form of their oxides, the moleratio of vanadium to molybdenum being between about 20:1 and about 1:20.

19. A process for the oxidative dehydrogenation of n-butane, whichcomprises contacting n-butane and oxygen in a reaction zone at atemperature of between about 1100 F. and about 1200 F. with a catalystcomprising aluminum phosphate doped with about 5 mole percent ofvanadium in the form of its oxide.

References Cited by the Examiner UNITED STATES PATENTS 2,440,236 4/ 1948Stirton 260-6833 2,441,297 5/1948 Stirton 260 683.3 2,942,932 6/1960Elliott 23-22 3,177,151 4/1965 Calvert 252437 X DELBERT E. GANTZ,Primary Examiner. G. E. SCHMITKONS, Assistant Examiner.

1. A PROCESS FOR THE OXIDATIVE DEHYDROGENATION OF ALIPHATICHYDROCARBONS, WHICH COMPRISES CONTACTING AN ALIPHATIC FEED AND OXYGEN INA REACTION ZONE AT A TEMPERATURE OF BETWEEN ABOUT 900*F. AND ABOUT1300*F. WITH A CATALYST COMPRISING A MAJOR AMOUNT OF ALUMINUM PHOSPHATEAND A MINOR AMOUNT OF A HEAVY METAL OXIDE SELECTED FROM THE GROUPCONSISTING OF (A) MOLYBDENUM OXIDE, (B) VANADIUM PENTOXIDE, AND (C) ACOMBINATION OF (A) AND (B).
 11. AN OXIDATIVE DEHYDROGENATION CATALYSTCONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF ALUMINUM PHOSPHATE AND AMINOR AMOUNT OF A HEAVY METAL OXIDE SELECTED FROM THE GROUP CONSISTINGOF (A) MOLYBDENUM OXIDE, (B) VANADIUM PENTOXIDE, AND (C) A COMBINATIONOF (A) AND (B).